I hate that this became a part of the marketing. It's not more than 100% efficient. It's more than 100% efficient if you compare how much energy the pump uses to heat a room (electric energy) to how much energy it takes to heat that room (heat energy). But those aren't the terms that we use to determine efficiency. Efficiency is determined by how much energy it takes to perform the task using the same method we're currently using in some "perfect" system (no energy loss due to friction, heat transfer, etc) and dividing that by how much energy we actually used.
A heat pump isn't heating the air, so it's unfair to determine efficiency by how much energy it takes to heat the air. It's moving heat energy from a low energy area (outside) to a higher energy area (inside) and that heat energy, plus some waste heat from running the compressor, is what's actually heating the room. But that isn't more than 100% efficient. In fact, heat pumps have grown in efficiency significantly over the last few decades because they haven't reached 100% efficiency.
It is accurate to say that any heat pump is going to be more energy efficient than any other type of furnace, but that's because they're doing different things. Just like an LED is going to be more efficient than any other lighting in terms of energy use. Again, different things. Though the heat pump and LED are pretty similar in what they're doing.